All living subjects maintain a reducing environment within their cells. However, due to the aerobic metabolism by the mitochondria and other factors reactive oxygen-derived species such as peroxides and free oxygen radicals are produced. The reducing environment is preserved by enzymes such as superoxide dismutase, catalase and glutathion peroxidase. If the normal redox state is disturbed, the reactive oxygen species may damage all components of the cell, including protein, lipids and especially DNA. This imbalance between the production of reactive oxygen species and the ability to detoxify the reactive intermediates or repair the damage caused by the reactive oxygen species is called oxidative stress.
In humans, oxidative stress is an important factor in aging and degenerative diseases associated with aging such as cancer, arthritis, diabetes, atherosclerosis, Lou Gehrig's disease, Parkinson's disease, heart failure, Alzheimers's disease, and Huntington's disease. The free-radical theory of aging states that organisms age because cells accumulate damage caused by reactive oxygen species over time.
A few strains of lactic acid bacteria with antioxidant properties are known in the art. For instance, U.S. Pat. No. 6,884,415 disclose an antioxidant food product produced by fermenting a food product containing a L. plantarum strain having Mn-catalase activity, in the presence of a manganese-containing natural material. The antioxidant properties of this strain depend on the presence of manganese. WO 03/002131 discloses a L. fermentum strain (ME-3) and its use as an anti-oxidative probiotic. WO 00/20013 discloses the use of Lactobacillus or Propionibacterium strains giving rise to increased amounts of propionic acid in the gut for reduction of the level of oxidative stress factors such as IL-6, reactive oxygen species and adhesion molecules. A preferred strain disclosed in this document is Lactobacillus plantarum 299v.
Ikeda et al, (2007, AEM 73:6404-6409) compared the life-span and Salmonella resistance of C. elegans worms fed with lactic acid bacteria (lactobacilli and bifidobacteria) with those of worms fed Escherichia coli OP50 (the standard food for C. elegans). They report that all the lactobacilli or bifidobacteria tested have a similar effect in increasing the life-span and Salmonella resistance when compared to E. coli OP50. However, the effect of lactic acid bacteria on worms submitted to oxidative stress was not assessed.